- RNA Granules in Germ Cells
- “Germ granules” are cytoplasmic, nonmembrane-bound organelles unique to germline.
- germ granules appear as dense, fibrillar structures that in some cases appear to have distinct subcompartments
- Balbiani bodies, consisting of ER and mitochondria interspersed with nuage surrounding Golgi stacks
- During meiosis, spermatocytes assemble a unique type of germ granule called the chromatoid body
- Two main classes of cytoplasmic RNA granules have been described in somatic cells: processing bodies and stress granules (Balagopal and Parker 2009). Processing bodies (P bodies) and stress granules share components implicated in RNA storage, turnover, and translational regulation.
- germ granules might correspond to P bodies and/or stress granules
- Germ granules have also been implicated in the regulation of mRNA levels, by promoting either mRNA storage or mRNA turnover at specific developmental stages.
Cytoplasmic RNA granules in somatic cells - share components implicated in RNA storage, turnover, and translational regulation.
- Processing bodies - (P bodies) contain components of the mRNA decay machinery,
- Stress granules - contain TIA proteins, poly-A binding protein, and stalled translation initiation complexes
Biol Reprod. 1970 Feb;2(1):129-53. Observations on the fine structure and relationships of the chromatoid body in mammalian spermatogenesis. Fawcett DW, Eddy EM, Phillips DM. PMID 4106274
- chromatoid body relocalizes to the base of the flagellum in elongating spermatids (Fig. 2C), and disassembles later during spermatogenesis
- Nuage (or commonly known as chromatoid body in mammals) is a conserved germline-specific organelle that has been linked to the Piwi-interacting RNA (piRNA) pathway.
- Vasa (known as Mouse Vasa Homolog in mouse), a nuage component, plays a mitotic role in promoting chromosome condensation and segregation by facilitating robust chromosomal localization of condensin I in the Drosophila germline.
- activator proteins called Cdc20 and Cdh1 are required for both APC/C activation and substrate selection
- APC/C mediated proteolysis of key regulatory proteins drives the cell from G2 through M phase into G1
- To enter the meiotic program, cells exit the cell cycle early in G1 before the accumulation of the G1 cyclins
Nature Mitosis and Cell Division
Cell Press Videos
Polymerization Pulls (George von Dassow, University of Oregon) http://www.youtube.com/watch?v=W89cD0YkHfw&feature=player_embedded http://www.youtube.com/v/W89cD0YkHfw
Ready, Set, Replicate (Teresa Davoli, Eros Lazzerini Denchi, Titia de Lange) http://www.youtube.com/watch?v=gucJ9TwHNtA&feature=player_embedded http://www.youtube.com/v/gucJ9TwHNtA